BTW, and unstable knee is most commonly attributed to an ACL injury of some sort…And ligaments will not heal on their own.
Obviously none of us are capable of diagnosing your injury, but if you have health insurance, go to the doctors.
As for pain, go with Ibuprofen. 600-800mg’s every 6 hours or so should be a safe amount if only taken for a short period of time as well. It will reduce the swelling as well.
Disclaimer - I am not a doctor, I just regular load up on painkillers during the winter to be able to keep skiing thru the pain.